Translation

How does protein synthesis fit into the Central Dogma of Molecular Biology?

It states genes flow from DNA to RNA to protein and synthesis helps translation so that flow can happen.

What role does RNA play in protein synthesis?

RNA carries out all of the genetic instructions from the DNA to the ribosomes.

What are the five main players in protein synthesis?

DNA: stores genetic information, mRNA: messenger to ribosomes, tRNA: transfers information to specific codons and amino acids, rRNA: structures ribosome, Ribosomes: where protein synthesis occurs.

What are the special features of the genetic code in relation to protein synthesis?

The triple codons; three nucleotides correspond to a single amino acid.

Why is the genetic code considered 'almost' universal?

Almost all living organisms use these codons but some species differ in stop codons.

What advantage does having multiple codons for individual amino acids provide?

It acts as a buffer to help prevent mutation by providing multiple coding options for the same amino acid.

What impact does shifting the reading frame have on DNA transcription?

It causes a frameshift mutation that changes how DNA is read, leading to different amino acids being created.

How do mRNA molecules differ in prokaryotes and eukaryotes?

Prokaryotic mRNA is polycistronic (multiple proteins) while eukaryotic mRNA is monocistronic (one protein).

In which direction is mRNA read during translation?

It is read from the 5’ end to the 3’ end, starting at AUG and stopping at a stop codon.

How are monocistronic and polycistronic mRNAs distinguished?

By the number of proteins they can create and the ribosome binding site, with monocistronic having no cap and no tail.

What is the advantage of polycistronic mRNA in bacteria?

It allows for rapid production of multiple proteins using less energy.

What are the main structural features of tRNA?

The cloverleaf shape with three loops, an amino acid attachment site, and an anti-codon loop.

What is the purpose of the CCA on the 3’ end of a tRNA?

It serves as the site where the amino acid attaches.

How do unusual bases in tRNA arise and why might they be important?

They arise through post-transcriptional modifications and may enhance the stability and function of tRNA.

What is the most variable portion of a tRNA molecule?

The anticodon loop.

How do codons and anticodons interact in relation to tRNA and mRNA?

Codons on mRNA pair with the corresponding anticodons on tRNA, aligning them for translation in a complementary manner.

What is the 'wobble' hypothesis?

It proposes that the third base of a codon can be flexible, allowing a single tRNA to pair with multiple codons for the same amino acid.

Can a given tRNA carry more than one type of amino acid?

No, each tRNA is specific to one type of amino acid.

Can different tRNAs accept the same amino acid?

Yes, different tRNAs can recognize the same amino acid due to redundancy in the genetic code.

What are the main distinguishing features of different tRNA molecules?

Differences are found in their anticodons and amino acid specificity.

Can a given tRNA molecule recognize more than one mRNA codon? Why?

Yes, due to the wobble position allowing flexibility in base pairing.

How are tRNA molecules attached to the correct amino acid?

Through the action of aminoacyl-tRNA synthetase enzymes.

What is meant by a charged tRNA?

A tRNA that has an amino acid attached to it is called a charged tRNA.

What distinguishes the ester bond connecting an amino acid to tRNA?

The bond is formed between the carboxyl group of the amino acid and the hydroxyl group of the tRNA.

How does aminoacyl-tRNA synthetase select the correct amino acid for tRNA attachment?

It recognizes the specific structure of both the tRNA and the amino acid, ensuring accurate attachment.

How critical is the function of aminoacyl-tRNA synthetase to cell function?

It is vital, as errors can lead to the incorporation of incorrect amino acids into proteins.

What components make up a fully functional ribosome?

Both protein and rRNA components.

What is the function of RNA components in ribosomes?

They are thought to be essential for catalyzing peptide bond formation and providing the structural framework.

In which direction does a ribosome read an mRNA molecule?

It reads the mRNA from 5’ to 3’, producing the polypeptide starting from the N-terminus.

What are the major steps in protein synthesis?

Initiation, elongation, and termination.

What is the sequence of events leading to the initiation of prokaryotic protein synthesis?

Involves binding of mRNA to the small ribosomal subunit, recognition of the start codon, and recruitment of the initiator tRNA.

What is the 'Shine-Dalgarno' sequence?

A ribosomal binding site in prokaryotic mRNA that helps initiate translation.

What are the A site, P site, and E site in a ribosome?

A site: where incoming tRNA binds; P site: holds the growing polypeptide; E site: where empty tRNA exits the ribosome.

What are the major steps in the elongation phase of protein synthesis?

tRNA binding to the A site, peptide bond formation, and translocation of the ribosome.

What drives tRNA binding to the ribosome?

Base pairing between codons and anticodons.

What drives peptide bond formation?

The catalytic activity of rRNA in the ribosome.

What are the main steps to the termination of prokaryotic protein synthesis?

Recognition of stop codons, recruitment of release factors, and disassembly of the ribosome.

How does a release factor terminate protein synthesis?

By binding to the stop codon, facilitating the release of the polypeptide chain.

What is a polyribosome and its advantage to a cell?

It is a complex of multiple ribosomes translating the same mRNA, allowing for rapid protein synthesis.

What are the main differences between protein synthesis in prokaryotes and eukaryotes?

Differences include the location, initiation mechanisms, and ribosomal structure.

Can polyribosomes form in eukaryotic cells? What are the advantages?

Yes, they allow for faster and more efficient translation of mRNA into proteins.